1. Field of the Invention
This invention relates generally to a device placed in a sewer pipe to trap articles which may plug the pipe. In particular, this invention relates to a guard with self cleaning features having special applications to toilets in prisons and other correctional facilities.
2. Prior Art
The desirability of providing a guard in a drain pipe or sewer pipe to trap articles which would otherwise clog the pipe has long been recognized in the prior art. With regard to a sewer pipe leading from a toilet, the requirement of a guard is that the ordinary solids introduced into a toilet, excrement and tissue paper, should be allowed to pass unobstructed while articles not readily decomposed, such as cloth, diapers, sanitary napkins and plastic, should be trapped. The aforementioned requirement are particularly stringent in the prison setting. Prisoners are prone to introduce cloth and paper into the toilets with the intent that the prison sewage system be caused to fail. Especially damaging is cloth or other material which, even if it does not clog the pipes, is not broken down or digested in the treatment plant.
Various stationary devices have been employed in sewer lines to trap undesirable articles as shown in the following U.S. patents.
______________________________________ Lehmann 2,693,603 Click et al. 2,811,724 Sierzega 3,904,523 Halstad 4,307,476 ______________________________________
Several of these inventions disclose devices with hooks which are positioned in the sewer line. However, because these devices are stationary, there is a tendency for otherwise safe waste, especially toilet paper, to accumulate on the hooks. Eventually, the line plugs at the site of the guard device.
Devices which rotate within a pipe to scrape the interior of the pipe or pulverize solids have been employed with some success. Examples of rotating guards may be found in the following U.S. patents.
______________________________________ Hirrich 1,217,763 Peaden 2,454,884 Hirshstein 2,627,610 Moore 3,439,361 ______________________________________
In a prison setting, however, where material and garments are introduced into the sewage system, additional burdens are placed upon the comminuting devices. For example, even the most powerful in line device disclosed in the prior art would have difficulty pulverizing a bed sheet.